Question

The effective resistance between $E$ and $F$ is

• A. $R/2$
• B. $R/3$
• C. $R$
• D. $noneofthese$

Answer 1

The correct option is A $R/2$

If we connect battery between E and F, then A,B,C, and D will be all at the same potential and the equivalent circuit is shown in the figure.
The equivalent resistance for each parallel branch is $R_p=(1/R+1/R+1/R+1/R{)}^{-1}=R/4$
The equivalent resistance between E and F is $R_{EF}=R_p+R_p=\left(R/4\right)+\left(R/4\right)=R/2$